There are recent demands to reduce the weight of engines for further improvement in fuel efficiency. Various structures, one typical example of which is an engine housing, are becoming less rigid as they become more compact and lighter. As a result, the engine housing undergoes greater deformation during engine operation. In these engines, a bearing member is held by a housing. When the housing and the bearing member undergo greater deformation daring operation, macro slipping occurs between the outer peripheral surface of the bearing member and the inner peripheral surface of the housing which may cause fretting damages. Thus, JP H10-159853 A and JP 2006-63995 A teach reducing relative micro slipping between the bearing member and the housing by surface roughening at least either of the outer peripheral surface of the bearing member and the inner peripheral surface of the housing.
However, while surface roughening reduces relative micro slipping, it is also prone to excessively increase the frictional resistance between the outer peripheral surface of the bearing member and the inner peripheral surface of the housing. The bearing member, being circumferentially divided, is pushed together so as to be squeezed from its outer peripheral side by the housing when being assembled with the housing. The bearing member is thus, secured to the housing. The outer diameter of the bearing member is designed to be slightly greater than the inner diameter of the housing. Hence, the bearing member is secured tightly with the housing by being squeezed by the housing from its outer peripheral side. However, excessive frictional resistance exerted between the outer peripheral surface of the bearing member and the inner peripheral surface of the housing inhibits even a small amount of overall or general movement of the housing and the bearing member when the bearing member is assembled with the housing. As a result, the stress applied to the divided bearing members by the squeezing of the housing concentrates at the interface, where the divided bearing members are put together, without being distributed throughout the bearing members. Thus, the bearing members deform largely in the vicinity of the interface, where the divided bearing members are put together, causing the bearing members to protrude toward the inner peripheral side at the vicinity of the interface. The bearing members protruding toward the inner peripheral side causes local contact with the counter member, which may be a shaft, during bearing device operation. Such local contact may produce heat and possibly cause damages to the engine.